The invention relates to a guide apparatus for copy masters.
Guiding devices of this type are already in use particularly in the automatic processing of photographic copy masters in printers. In such printers usually copy masters in the form of individual positive or negative film strips are initially spliced into a long strip of film. This strip is then conducted to a measuring station wherein it is measured. After measuring, the necessary quantities of copying light are determined and subsequently the desired image fields of the film strip are copied onto a photosensitive photographic copy material, for example photographic paper.
On the film strips spliced into a single strip of film, commercially available information concerning the corresponding image field, the type of film, etc. is present in the lateral edge zones or portions of the individual strips, which may be taken into consideration for example in the determination of the quantities of copy light required. Usually, the so-called DX code is applied. It contains information relative to the film product, the type of film and, in the case of many manufacturers, information concerning the image number. This information is present most often in the form of one or two track bar codes applied in the longitudinal direction of the film relative to a lateral edge zone of the film strip. Depending on the manufacturer, occasionally the image field number is also shown in the form of a bar code. Such bar codes in the case of commercial films include for example two tracks, a data track and a cycle track, which are formed purely externally of similar elements (bars). However, they have different functions and different combinations of the individual elements (bars). A measuring cycle is produced by means of the cycle track, whereby the mostly coded data of the data track can be read, the data track containing the information (data) proper in a coded form. To produce the cycle, the cycle track is exposed for example to red light, for example by means of red LED-s, and the transmitted light received on the other side of the film, for example by means of a photodiode, converts the optical signal received into an electric signal. By means of the transparent and non-transparent elements (bars) in the cycle track, the cycle is produced in this manner. The data of the data track are read in the same manner (exposure of the data track., measurement of the light received on the other side of the film). These data are then available as the input data for decoding.
Within the measuring station a defined lateral guidance of the film is required, as during the measurement of the image fields a definite position of the image field to be measured is necessary so that the measuring process may be carried out. The same is true for the reading of the data in the lateral edge zone or portion of the film strip. For this purpose, in known devices, the film strip or band is "forced" by guiding elements along a defined path. These guide elements comprise two stationary lateral walls extending approximately perpendicular to the transport plane of the film strip and parallel to the direction of transport. Between these lateral walls the film strip is guided by its lateral edges. In order to be able to read the bar code (DX code) in the lateral edge zone of the film strip, detection means are provided (for example LED-s and photodiodes, as set forth above).
This type of guidance (also called "hard" guidance) is usable in itself, but has certain disadvantages. For example, this type of guidance cannot react to variations in the width of the film strip to be processed. Such width variations may, for example, be due to manufacturing conditions (over or under dimensioning of the individual film strips). They may also be due to the splicing of several film strips into one long film strip. Excessive widths may be caused, for example, by the excessive width of the splice itself, but also by inaccuracies in the splicing of the film strip. For example, two film strips may be spliced together slightly offset relative to each other or they may be spliced at a slight offset angle to each other. In both cases, this results in variations of the width of the film strip produced by splicing.
This film strip is forced in the measuring station into the abovedescribed "hard" guide. This may lead, in the case of an excessive width (regardless of the cause) of the film strip, to problems in transportation, caused by the increased friction of the lateral edges of the film strip on the lateral walls. This may result on the one hand in a higher wear of the lateral walls by the film strip edges rubbing against them, and on the other hand, in damage to the film strip. In addition, impediments during transportation may cause appreciable fluctuations in synchronization during processing, which cannot be tolerated. Furthermore, the film strip may be bent in such areas of excessive width, so that the reading of the DX code or the measuring of the individual image fields become difficult or even impossible.